The present invention relates to a clutch or a coupling transfer device between an input shaft and an output shaft, which functions automatically in each of the two rotational directions, when the difference of speeds (resulting from the mechanical structure) between the output shaft and the input shaft reaches a certain value, the control for the actuation of the device being connected to the control for the direction of rotation or drive.
In the field of automotive vehicles, devices are known for coupling the rear axle with the front axle in the case of a front drive vehicle, or for coupling the front axle with the rear axle in the case of a rear drive vehicle. These devices are generally mechanical dog clutch systems. These systems are disposed on the transmission shaft in two parts, connecting to the two axles. Despite tapering of the clutch's teeth these devices require control of the dog clutch during stopping.
Such known devices have many disadvantages. Specific manual control of the dog clutch is necessary, thus requiring a control lever in addition to a speed control lever. It is a mechanical system which is expensive to manufacture. Sustained attention of the driver to the performance of his vehicle is required in order to decide whether the clutch should be engaged.